Comprehensive Income (Loss) - Reclassifications (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Reclassification Out of Accumulated Other Comprehensive Income (Loss) [Line Items]
Fuel and oil	$ 1,547	$ 1,004
Less: Tax expense	(46)	(98)
Interest expense	66	93
Net loss	(159)	$ (278)
Reclassification to earnings
Reclassification Out of Accumulated Other Comprehensive Income (Loss) [Line Items]
Net loss	(20)
Fuel derivative contracts | Fuel and Interest Rate Derivatives | Reclassification to earnings
Reclassification Out of Accumulated Other Comprehensive Income (Loss) [Line Items]
Fuel and oil	(28)
Less: Tax expense	(6)
Net loss	(22)
Interest rate derivatives | Fuel and Interest Rate Derivatives | Reclassification to earnings
Reclassification Out of Accumulated Other Comprehensive Income (Loss) [Line Items]
Less: Tax expense	0
Interest expense	2
Net loss	$ 2